The best source for floor speech is the Congressional Record (and in general, official government sources; the site you linked is not official, and official US government sites have URLs ending in .gov or .mil). The relevant parts on the floor of the full House are from Dec. 3 and Dec. 4 which had the actual vote. The full official legislative timeline is here.
The committee markup itself has no text transcript I can find; the video record is at the Committee on Foreign Affairs's website. At first glance, it seems like the meeting was roughly pro forma, and the resolution was amended and reported back by unanimous consent. Update: I listened to pretty much the whole thing; it has no real debate of substance, since they weren't handling anything controversial.
Summary: They don't seem to have been presenting detailed proofs with evidence, because: this is pretty much universally accepted in the US (the idea that it was not Russian-supplied SAMs is generally dismissed as Russian propaganda), and because Congress doesn't always feel the need to formally investigate every single aspect of what goes before it (particularly when it's noncontroversial; investigation that does happen is often done informally, and it seems unlikely that anyone would object to that line because it's utterly uncontroversial here), and because an H.Res. is not actually binding in any way (it is not a law, nor can it become a law, nor is it intended to be anything more than an expression of opinion by the House).
To answer the question in the title (instead of in the body), the right source is an official government one, not an unofficial .us domain, nor C-SPAN (which is also not part of the government). The official record of proceedings on the floor is the Congressional Record, which is available to the general public for free on Congress's website. Committees are not all in the official Congressional Record; they have their own records, which may or may not all be posted online. If they aren't online, contact the committee to ask for them -- there's nothing really to lose, and if the meeting wasn't closed, you'll probably be able to get a copy.
There is one major exception: when considering confidential information, committees will hold closed sessions so they can discuss classified information without revealing it to the public. This will obviously not be released to you (though it didn't seem to happen in this case), and these meetings will be closed to the public (you can go to normal committee meetings and floor debates; closed meetings are the exception). Each house can also go into secret session, which means that the transcript of the floor meeting (normally in the Congressional Record) is not published (and all spectators are escorted out). This happens very rarely for the House, but more often for the Senate. In this case, the transcript is obviously not available.
Note: The Congressional Record is the official record, not a transcript. It can be amended, and written things can be put straight in the record if no one objects. But that tends to be done to add rhetoric, not to remove things (and unlike in some state legislatures, members of Congress cannot change votes after the fact to my knowledge, except in one or two cases in the House where a single member can change their vote for procedural reasons [i.e. they have to be on the winning side to propose some necessary motion, but it's clear what they actually supported]).